Papillomaviruses (PVs) have been shown to contribute to the pathogenesis of cancer of the cervix, vulva, penis, oral mucosal sites and skin. Immunity to these viral infections plays a significant role in disease outcome, but the precise viral targets of immunity for prevention of infection and destruction of active lesions in vivo are poorly characterized. Our long-range goal is to determine which viral antigens and immune effector cells are involved in a successful immune response to PV infection. The objective of this application is to examine immunity during three stages of human papillomavirus type 11 (HPV-11), HPV-16, cottontail rabbit papillomavirus (CRPV) and rabbit oral papillomavirus (ROPV) infection. The first stage is represented by antibody-mediated virus neutralization which targets surface conformational, type-specific epitopes located in the hypervariable regions of the major coat protein (L1) of papillomavirus proteins, and linear epitopes on the minor coat protein (L2). The second stage is cell-mediated immunity to (peptide) epitopes of processed and MHC-associated early viral proteins present in infected epithelial cells. The third stage of immunity will assess host cell-mediated responses that lead to spontaneous regression of papillomas. Our recent studies demonstrate clearly that there are different viral target proteins and immune effectors at each of these different stages. The central hypothesis to be tested is that immunity to PV proteins can lead to protection and resolution of the disease. The rationale behind the research is that studies on viral immunity will provide essential information for the design of protective vaccines and immunotherapeutic interventions for HPV infections. To accomplish the objectives of this application, we will pursue two Specific Aims: (1) define the nature of the components of conformational and linear neutralizing epitopes on papillomavirus virions involved in protective immunity to infectious virions, (2) determine the natural and induced host cell-mediated immunity to CRPV using CRPV genomes with genetically modified E6 genes that follow predicted outcomes of either natural regression or persistence. At the completion of this research, we expect to have mapped critical amino acid residues on HPV-11, -16, CRPV and ROPV virions (both L1 and L2) that are recognized by a panel of neutralizing monoclonal antibodies (N-Mabs). In addition, we plan to utilize a large number of genetically altered CRPV genomes (altered amino acid residues in the E6 gene) to dissect the host immune response leading to regression and persistence of CRPV-induced infections. Defining the major protective viral epitopes on papillomavirus virions and on the early viral protein, E6 in papillomavirusinfected cells will be key to planning effective immunotherapeutic management of this infectious disease.